Effects of varying dietary iodine supplementation levels as iodide or iodate on thyroid status as well as mRNA expression and enzyme activity of antioxidative enzymes in tissues of grower/finisher pigs.

PURPOSE: The objective of this study was to investigate the influence of high dietary iodine supply and different iodine sources on thyroid status and oxidative stress in target tissues of the thyroid hormones in fattening pigs. METHODS: Eighty castrates (body weight: 33.3 ± 0.4 kg) were randomly allotted into five different treatments: The control diet contained 150 µg I/kg as KI, the other feeding groups were supplemented with 4,000 µg I/kg (as KI and KIO(3)) and 10,000 µg I/kg (as KI and KIO(3)), respectively. The mRNA expression levels of sodium/iodide symporter (NIS) and key antioxidant enzymes (Cu/Zn SOD, CAT, GPx) were analyzed in thyroid gland, liver, kidney, muscle, and adipose tissue sampled during slaughter. Furthermore, antioxidant enzyme activities and the effect on lipid peroxidation (MDA) were determined in liver and muscle. RESULTS: In thyroid gland, a significant downregulation of NIS and Cu/Zn SOD mRNA expression was observed in high-iodine groups. In liver, a source effect on the mRNA expression of Cu/Zn SOD between KI and KIO(3) at 4,000 µg I/kg was shown. In contrast, not SOD but GPx activity was affected by iodine source with strongest downregulation in high KIO(3) group. In muscle, GPx activity was affected by both iodine source and dose, showing stronger downregulation in KI groups. In kidney and adipose tissue, oxidative stress parameters showed no or only unsystematic changes. However, variation in iodine supply had no effect on MDA concentrations. CONCLUSIONS: NIS expression was significantly decreased with increased iodine supplementation, which is to ensure the thyroid gland function. However, the alleviating effect of iodine supplementation observed in antioxidant enzyme mRNA expression and activity did not reflect on the lipid peroxide level.

Effect of iodine source and dose on growth and iodine content in tissue and plasma thyroid hormones in fattening pigs.

PURPOSE: The aim of the present feeding trial with iodine was to assess pigs' growth performance and carcass characteristics, the iodine accumulation in tissues, and their influences on the thyroid hormones in plasma. METHODS: Eighty pigs (33-115 kg body weight) were allotted to 5 dietary treatments: a control group (150 µg I/kg), two potassium iodide [KI] groups (4,000 and 10,000 µg I/kg), and two potassium iodate [KIO3] groups (4,000 and 10,000 µg I/kg). Iodine concentration was determined in thyroid gland, liver, kidney, muscle, fat, and skin by ICP-MS. Furthermore, thyroxine (T4) and triiodothyronine (T3) in plasma were evaluated. RESULTS: High dietary iodine tended to have a negative effect on younger animals' growth (average daily gain, ADG). However, during the entire growth period, the growth performance and carcass characteristics were not influenced by iodine dosages or sources. Irrespective of iodine source, higher iodine doses of diets affected higher iodine stores in all tested tissues except for abdominal fat. Thus, iodine supplementation with 10,000 µg I/kg feed significantly increased iodine content in thyroid gland (+122%), liver (+260%), kidney (+522%), muscle (+131%), and skin (+321%) compared to the control group. However, there was no significance of thyroid hormones in plasma. CONCLUSIONS: As a result, pork and fat of pigs showed only low iodine accumulation even in the high-iodine groups. Thus, there should be no risk of an iodine excess in human nutrition and animal health, and the EU-upper level for iodine in pig feed can be maintained.

Evaluation of potential reference genes for relative quantification by RT-qPCR in different porcine tissues derived from feeding studies.

Five potential reference genes for RT-qPCR application, namely histone H3, beta-actin, GAPDH, ubiquitin and 18S rRNA, were evaluated for normalization of gene expression in four selected tissues (liver, kidney, thyroid and abdominal fat). Tissues were derived from fattening pigs exposed to different amounts and type of dietary iodine. Two software applications (geNorm and NormFinder) were used to evaluate the stability of the potential reference genes. All studied genes displayed high expression stability but different stability patterns between the investigated tissues. The results suggest GAPDH and 18S rRNA as reference genes applicable in all tissues investigated. Beta-actin and histone H3 are suitable reference genes for all tissues investigated except fat. In contrast, ubiquitin should be excluded from use as a reference gene in the porcine tissues analyzed due to variations in expression levels, despite the good expression stability.

Susceptibility of bifidobacteria of animal origin to selected antimicrobial agents.

Strains of the genus Bifidobacterium are frequently used as probiotics, for which the absence of acquired antimicrobial resistance has become an important safety criterion. This clarifies the need for antibiotic susceptibility data for bifidobacteria. Based on a recently published standard for antimicrobial susceptibility testing of bifidobacteria with broth microdilution method, the range of susceptibility to selected antibiotics in 117 animal bifidobacterial strains was examined. Narrow unimodal MIC distributions either situated at the low-end (chloramphenicol, linezolid, and quinupristin/dalfopristin) or high-end (kanamycin, neomycin) concentration range could be detected. In contrast, the MIC distribution of trimethoprim was multimodal. Data derived from this study can be used as a basis for reviewing or verifying present microbiological breakpoints suggested by regulatory agencies to assess the safety of these micro-organisms intended for the use in probiotics.

Antibiotic susceptibility of members of the Lactobacillus acidophilus group using broth microdilution and molecular identification of their resistance determinants.

The range of antibiotic susceptibility to 13 antibiotics in 101 strains of the Lactobacillus acidophilus group was examined using the lactic acid bacteria susceptibility test medium (LSM) and broth microdilution. Additionally, microarray analysis and PCR were applied to identify resistance genes responsible for the displayed resistant phenotypes in a selection of strains. In general, narrow as well as broad unimodal and bimodal MIC distributions were observed for the Lactobacillus acidophilus group and the tested antimicrobial agents. Atypically resistant strains could be determined by visual inspection of the obtained MIC ranges for ampicillin, chloramphenicol, clindamycin, erythromycin, quinupristin/dalfopristin, streptomycin and tetracycline. For most of these atypically resistant strains underlying resistance determinants were found. To our knowledge erm(A) was detected in lactobacilli for the first time within this study. Data derived from this study can be used as a basis for reviewing present microbiological breakpoints for categorization of susceptible and resistant strains within the Lactobacillus acidophilus group to assess the safety of microorganisms intended for use in food and feed applications.

Inulin and probiotics in newly weaned piglets: effects on intestinal morphology, mRNA expression levels of inflammatory marker genes and haematology.

The study aimed at determining the effect of inulin and/or a multispecies probiotic formulation on gastrointestinal tract (GIT) morphology, immunological and haematological parameters. Forty-eight newly weaned piglets were assigned to four feeding groups, receiving a standard basal diet (control), supplemented with 0.4% inulin, probiotics (1 x 10(9) CFU/kg as fed, enterococci, lactobacilli, bifidobacteria) or a combination of both (synbiotic). After four weeks of ad libitum feeding piglets were slaughtered and intestinal tissue samples were obtained for histometry. Additional tissue samples of the GIT, mesenteric lymph nodes, blood, liver and spleen were taken for mRNA expression analysis of cell turnover (CDK4, caspase3, IGF I), transcription factor NFkappaB and inflammatory marker genes (TNFalpha, TGFbeta). Changes in histometry occurred predominantly in the small intestine, showing higher jejunal villi when probiotics were administered alone (p < 0.10). Inulin decreased the number of acidic goblet cells in jejunal villi (p < 0.05), whereas probiotics increased neutral goblet cells in ileal villi (p < 0.05). Though inflammatory marker genes were uninfluenced by treatment in the proximal GIT, the colon showed downregulations induced by inulin (TNFalpha: p < 0.10, TGFbeta: p < 0.05). Gene expression of CDK4 was upregulated in the jejunum and of TGFbeta in the mesenteric lymph nodes in the probiotic groups. Interestingly, the probiotic group alone exhibited upregulations in cell turnover marker genes in the colon and blood. Furthermore, for numerous parameters, inulin and probiotics led to no synergistic but antagonistic interactions.

Comparison of broth microdilution, Etest, and agar disk diffusion methods for antimicrobial susceptibility testing of Lactobacillus acidophilus group members.

In recent years, the absence of acquired antimicrobial resistance has become an important criterion to evaluate the biosafety of lactobacilli used as industrial starter or probiotic cultures. At present, however, standards for susceptibility testing of Lactobacillus strains or approved guidelines for interpreting the test results are not available. Hence, this study was carried out to contribute to the establishment of a standardized procedure for antimicrobial susceptibility testing of lactobacilli. The results obtained by testing 104 strains of the Lactobacillus acidophilus group were compared based on broth microdilution, disk diffusion, and Etest. Except for some specific agent-related effects, agreement between MICs resulting from the broth microdilution method and the Etest was good. In addition, inhibition zone diameters determined with disk diffusion correlated well with MICs from Etest and broth microdilution.

Antibiotic susceptibility testing of Bifidobacterium thermophilum and Bifidobacterium pseudolongum strains: broth microdilution vs. agar disc diffusion assay.

There is urgent need for having available suitable methods and data regarding the susceptibility levels of antibiotic resistant and sensitive strains of bifidobacteria. Based on a defined standard operation procedure, agar disc diffusion and broth microdilution were compared in order to evaluate the antimicrobial susceptibility profiles of 82 B. pseudolongum and 80 B. thermophilum strains mainly originating from the meat production chain. The methods that were assessed showed interpretable agreement within this study. The disc diffusion zone diameters are highly reproducible making the method a useful alternative to broth microdilution for antimicrobial susceptibility screening of bifidobacteria.

Antibiotic susceptibility of Bifidobacterium thermophilum and Bifidobacterium pseudolongum isolates from animal sources.

The widespread use of antimicrobial substances has led to resistant populations of microorganisms in several ecosystems. In animal husbandry, the application of antibiotics has contributed to resistance development in pathogenic and commensal bacteria. These strains or their resistance genes can be spread along several ecological routes, including the food chain. Antibiotic resistance is important in terms of the safety of industrial strains, such as probiotics for food and feed. Bifidobacterium thermophilum and Bifidobacterium pseudolongum are known to comprise the major part of the bifidobacterial microbiota in the gut and feces of cattle and pigs. In this study, the antimicrobial susceptibility in bifidobacterial isolates of these species was investigated. Isolates from the beef and pork production chain were identified and typed to strain level, and the antimicrobial susceptibility level was tested to a set of antibiotics. Isolates with low susceptibility levels were screened by PCR for already described resistance genes. Strains atypically resistant to clindamycin, erythromycin, and tetracycline were determined. The resistance genes tet(O), tet(W), and erm(X) were detected in the bifidobacterial species that were examined.